The invention relates to a filter which preferably is equipped with vertically disposed hole-like filter webs which are adapted to perform a movement in order to remove the filter cake.
An alluvial or matting filter of this type is known from the West German Pat. No. 1 007 294. The filter means or filter web in this case is formed as a bellows which is extendable in longitudinal direction. The interior of the bellows is supported or stiffened by means or resilient wire coils. If the stiffening elements are not provided the bellows can be pretensioned by means of a tension spring provided in its open bottom portion.
The drawback of this prior art product is that parts are required like coils or tension springs which are subject to mechanical stress and therefore are exposed to a high degree of wear and metal fatigue. The same fatigue phenomena appear also in the bellows themselves. Furthermore, the filtration can be disrupted since, for instance, in case of pressure changes through the mechanical parts forces are generated which may cause a premature fracture or dropping off parts of the filter cake.
It is therefore an object of the present invention to provide a filter which avoids these drawbacks and in particular which does not make use of a bellows to cause movement of the filter web in order to separate the filter cake.